1. Technical Field
The present invention relates to a technology for measuring the temperature of an electromechanical device without using a temperature sensor.
2. Related Art
An electromechanical device (an electric drive system) has been suppressing an amount of electrical current using the current feedback control within the rated current in order to operate within the rated current of the robot control and so on. Therefore, there has been no other robot control than the robot control slow in action and lacking an instantaneous force.
However, in recent robot control, it is conceivable that increasing importance is given to the instantaneous maximum torque characteristics of instantaneously performing the torque control with the torque N times as strong as the rated torque of the motor characteristics by applying a current N times as large as the rated current for a short period of t/N.
For example, a robot like a baseball player acts at a moderate speed in an ordinary motion, but in the case of coming to bat as a home run hitter, the torque with which the momentum several time through several tens of times as large as the normal momentum is applied to the thrown ball on the 0.1 second time scale is required to achieve the home run. Such a robot capable of generating the torque for the several tens of times of momentum for a short period is realized.
To that end, it is necessary to perform the torque (current) control for achieving the instantaneous maximum torque characteristics while monitoring the temperature in real time so that the temperature of a coil in an electric motor does not reach a predetermined temperature instead of controlling the amount of current from the beginning.
In essence, the performance of the motor is determined by the instantaneous maximum torque characteristics, and the method of preventing the temperature from reaching a predetermined level while monitoring the rise in temperature due to the copper loss, the iron loss, and the mechanical loss at that occasion becomes important.
In the magnet coil causing the copper loss, which is the most significant factor of the rise in temperature among these losses, it leads that the torque (current) control is freely performed within the assured temperature range.
Therefore, the explanation will be presented citing a coreless motor in which the iron loss is hardly generated and the rise in temperature due to the copper loss in the magnetic coil is dominant. Here, in order to measure the temperature of an electromechanical device, it is necessary to separately provide a temperature sensor as described in JP-A-2010-240952 (Document 1).
If it is attempted to directly measure the temperature of the magnetic coil with the copper loss, it is required to directly dispose a temperature sensor to the magnetic coil of the electromechanical device (the electric drive system) as described in Document 1. However, there arises a problem that it is difficult to prepare a space for directly attaching the temperature sensor to the magnetic coil.